This invention relates in general to irrigation equipment and deals more specificially with a system for controlling the guidance of a lateral move irrigation machine.
Mobile irrigation systems having elevated booms are generally classified either as center pivot machines or lateral move machines which are also referred to as linear or in line machines. In the center pivot machine, an upright stand pipe at the pivot point of the system supplies water to an elevated boom carried on wheeled towers. The towers are driven by drive motors in a circular path centered at the stand pipe, and sprinklers spaced along the boom apply water to the field. The lateral move irrigation system likewise has an elevated boom carried on mobile towers. However, instead of moving in a circular path, the towers of the lateral move system are usually driven in a straight line path which is perpendicular to the irrigation boom.
Although both types of irrigation system have been widely used and have performed well for the most part, the lateral move machine has various advantages over the center pivot machine which make the lateral move machine more desirable in many situations. With the center pivot system, considerable difficulty is encountered in applying adequate quantities of water to the corner areas of the square or rectangular fields in which the equipment usually operates. Also, more water must be delivered to the outer end of the irrigation boom than to the portions near the pivot since the outer portions of the boom cover more surface area.
Lateral move irrigation systems avoid these problems but are faced with others which have proven difficult to overcome. Perhaps most notably, accurate guiding of the lateral move machine through the field has presented considerable difficulty. Alignment systems such as that shown in U.S. Pat. No. 3,608,826 have been used for both center pivot machines and for lateral move machines and have been generally effective in maintaining the irrigation boom in a straight condition. Nevertheless, such systems are plagued by the types of problems which arise in connection with all mechanical devices. For example, the reliability of mechanical alignment devices is lacking somewhat, particularly after the parts have become worn due to prolonged use and exposure to the elements. Existing alignment systems are also characterized by undue cost and complexity which adds significantly to the overall cost of the irrigation equipment.
Additionally, existing alignment systems function only to maintain the boom in a straight condition. In lateral move machines, the entire boom can turn such that its direction of movement is angled relative to the intended direction of travel. Since this can occur while the boom remains substantially straight, conventional alignment systems are not effective to steer the machine back on course. If the irrigation machine departs appreciably from its intended course, the effectiveness of the irrigation suffers and in some cases the machine can move outside of the field and possibly cause serious damage to fences and other structures, as well as to the irrigation machine.
Guidance systems which have been proposed in the past for lateral move machines typically operate to sense the angular relationship of a support tower with respect to a reference line, such as a buried wire, an above ground cable, a furrow in the field, or a row of stakes. Due to the great length of the irrigation machine, small deviations in the angle of the tower cause large displacements at the end of the machine. Consequently, for effective guidance control, these systems must be extremely sensitive to the tower angular displacement in order to prevent undue displacement at the ends of the machine, and such sensitivity is difficult to achieve in actual practice.
It is the primary object of the present invention to provide an improved system for accurately guiding a lateral move irrigation machine along the intended path of travel with the irrigation boom maintained in a straight condition.
Another object to the invention is to provide a guidance system of the character described which avoids the mechanical problems associated with systems that employ mechanical linkages and the like. In this respect, it is noteworthy that the guidance system relies on fixed check points and does not depend on mechanisms on the irrigation machine that can lose their adjustment and develop other mechanical problems.
A further object to the invention is to provide a guidance system of the character described wherein the boom position is checked at regular intervals. In accordance with the invention, a series of spaced apart rows of check points are established at preselected locations in the fields, and the path of movement of the boom is automatically corrected when the irrigation machine reaches each row of check points. It is another important feature of the invention that the rows of check points can be spaced apart as desired to permit the boom position to be checked and corrected at various locations in the field.
An additional object to the invention is to provide a guidance system of the character described in which the drive motors of the irrigation machine are automatically energized to resume normal movement of the machine each time its path of movement has been corrected.
Yet another object of the invention is to provide a guidance system of the character described which is well adapted for use with various types and sizes of lateral move irrigation machines.
A still further object of the invention is to provide a guidance system of the character described which is simple and economical to construct and reliable in operation.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.